Internal focusing device



Nov. 25,1952 STEERS 2,619,607

INTERNAL FOCUSING DEVICE Filed March 10, 1951 I in I INVENTOR fillz'am FSleers ATTORNEY Patented Nov. 25, 1952 j W PNEENT' E? v I 2;e19;s07{-.

INTEKNAIZ.FOCUSINGDDEVIGE";

William E; ,steem lzivingston N. 1., ,assignor tU-E Glaser: Steers Corporation, Kelleville N; J1", a v corporation of Newiersey- AimlicwtionzMarehdO, 1951;. Serial :No; 21el;88!tv 'I'his. .inllention reletes toafoeusing'"devicesfor cathode.ra.y.= tubes and ymoreypanticulalizly, to the;

concentration of thefiuzc aklong ,theglbeaimu v fIfhecobjeetvof this invention iseto concentrate thegelectronibeam of, efc'aithode ray, tubelmorez efiectivel$.', Y 7

Another; object .iisgtb, provide, a: more uniform clistrilavutionpilthe;fluxin.focusing deyices,v

A'- stilltflirthen .Ob iCQt iSr-tOLPIDVidC. aflmagnetie focusing device: in which the 'flu-x is. brought clse tetheselectronbeaml..

Otherc'. and; further. objects, .will j appear, from; the fellowing specification.tekenuinpconnection. with;,the;accmpanyine;drawingsin which.

Fig", 1 is a view of the neck of'a cathovdesray, tuhe w.ith a sectional, presentation of, one item of the. invention; I

. andj. 4;arec sectional; viewswof Luther. formswiithe:invention...,

anode I 7 supported 'omg iassrrods I 8;whichtextend axiallyintheyneck I02". Afocusingwoilileiirthe; focusingde'vicer I 3 cooperateswith ,the magnetici ti-Claims; (c1. 3.1.3::84)

The-"rods .8 :which' zsuppertithezanodea I 1 5 1 7 1 nor-tedious thGQ-OfirthOdfi-J EIIW-hiCh inr ur m sezslmr ported mn} ther-base I I In the assembly; of the; tuhB-JhG-Emt R J; parts cofitheffocusing, dev ce A .3:-

- llrlfltherelectron gun; I2, are: assembled" and.)

meunted ,en the-:b'aserl .I, in rt z ndt sealed ins thfiinfifilizl (lofthetube: The-coil ,I 9 is'mo ntediin. an" annular, insulatin ;v Liner. 2 5., re nd h n ck; ID as, the;.outside componentgof the, fdeusing device I3; A,shell- 2;Lof.tmild steelencloses -the,

coil .=.I 9 ancleomnle srthe me n tieeircuitnutside the: coil.

The, eleetren elm of .i.e1ectrons which shoots, through the neck?) I O;

I of 'the'tube and against a fluorescent screen (not shown) c In :extending through the, neck I Ilsthe' electronstreameftert leaving he un I i lnes es throu h,lthefocusingqdeviceeI 3 andthenthrpugh; the. deflecting. yoke, I 5,, The stream. is: dirleet g; hrou hthedaperture-rlllg Direct urrentepassed; through .the'. oi-l I9;creates, t.masnetictfieldiwithi ther linesatoi I force, passin from. dise.,A to d ISQ- B.

hrough. the l n es 2 I; nd, xially acmssi he:- gelp 'L, I Thelines .o .force conducted .to gthjeap err. ture [s concentrate. the. field, near,- he; ele tmm heamendincreasesthe fiect;.0i; he fiel ion the; beams Bymeason .o.f..'the. flan es 2i carrying the lines? oticircefihe fiel L s uniformly, 'erran esii amund.theebeemrandnnifprmlsg effeetsthehe me Thus=then0le pieces; IMoi"thisinyentien-earry the: m ne i flux tithe,areae ii he, lwttQnbenm;

and. concentrate. its in, thie'.anerture .29; adja en thecentemf thebeemr polef-pieces I I to; producear focusing fieldin" a:

central passage 20'- through the; pole, piecesflfl; 'Ihepole pieces, I lfintFig-q 1 are, a;pair-oi-'discs-A* and-B each mademn .off'a: flezngedning ot which Adjustmentoi.thelfeeusr accomnlisliedwby variation, of the-cfiull i llti ill heeeoililai. I

A; manna Inn f; this inven ion s I shewniiri V Eign'lwhichevariationoi 'thefpcnsinsJ-devic'e;

together *and spaced a'pa-rt bynon magneticr shoulder rivets-2 2; Each rivet- -22 -ha-s--a-n enlarged I 3Q l fii the heels I I!v prod es. s. c n ntrat n j mbodiment; oi.iFig.. 1. is nplicaoleqtoc h modl:

centred section-"1'3 againstwhichthe-discsA and I fi'catien Qf Fig-3-2;: Inth o us n sdeyic 1 10f. liig,.,2f a, pa n. qfjdises Cfandi hav bliqu war-(11yextendingcfier e Qtherwiseth lSQ C'feniflare similar. t di s and; B:'0 f. j' The focusing cleyiceiI 3 'ofjEig 2 has a permanent magnet; 32f'aroundj the/outside of the. neck I0? enco nassinegtheidiscs. C'""and1 Th m mer n'ent; magnet 32 is. iormesi'nfi a suitablemateriaL andsmayl either bie iii rthenforlrls Qfan. lml llalring or single magnetsplace symmetrically arq ndthe, tube.- A shunting ring. 33 isfiplacedoaroundrand oventhemagnetBZ .in asliding fitl The shunting ring p33! is o spaced: from the. ma net 32, with. nommagnetie, luminum: or. br ss. s neratonz I 2 reat s! n; xial tream;

interposed between the ring 33 and this magnet 32. This ring 33 is made up of a mild steel or other suitable magnetic metal which when it moves with relation to the magnet 32 changes the field produced within the neck Ii] by the magnet 32.

In Fig. 2 the magnetic flux from the magnet is directed to the aperture 30 along the flanges 3|. At the aperture 30 a field is produced along the axis of the neck If} so as to focus the electron beam directed through the aperture 39. shunting ring 33 when overlying the magnet 32 decreases this magnetic flux and the field in aperture 30. The degree of this minimization of the focusing efiect is in direct proportion to the extent of the coverage of the magnet 32 by the ring 33, with the greatest magnetic efiect when the ring is completely removed.

In the modification shown in Fig; 3 the focusing device I3 is made up of a shunting ring 34 outside the neck Ill together with a pair of discs E and F, and an inside magnet 35 spacing the discs E and F within the neck H]. The disc E is a flat plate with a central aperture 35 at the center of the neck Ill. The disc F has a tubular central passage 31 aligned with central aperture 36 of disc E. The two discs are suitably fastened on the sides of the field producing magnet 35. The resultant unit formed by the two discs E and F and magnet 35 are supported on glass rods at one side and centered in the neck by fingers on the other side. The shunting ring 34 is movable axially along the neck ID to vary the amount of enclosure of the magnet by the shunting ring 34.

The magnetic flux of the magnet 35 is conducted by the discs E and F to the aperture 36 and tubular passage 31. The flux is thus concentrated in producing a field across the space G lying between the inner end of tubular passage 31 and the disc E. The stream produced by the electron gun 12 passing through the aperture 36 and the tubular passage 31 is focused by the field across G. The focusing adjustment of the device 13 in Fig. 3 is accomplished by positionin of the shunting ring 34. In a further modification the ring 34 may be omitted. The focus may be controlled by varying the second anode voltage when the internal magnet is of such a size as to provide a correct flux for a conventional tube at normal line voltages and normal anode voltages.

A still another modification of this invention is shown in Fig. 4. Discs H and J are shown'positioned within the tube neck [0 similar to the positioning of the discs in the embodiments of Figs. 1, 2, and 3. The discs H and J are incorporated in a focusing device which produces lines of force as described above. This focusing device may have either a focusing coil or a permanent magnet as the flux producing means. Each of the discs H and J have a radial portion 37 with a short axial flange 38 circumscribing a central aperture 39. The flanges 38 of the discs H and J face inwardly toward each other formin a gap K which is less than the distance between the radial faces of the portions 31. The discs H and J are held together and separated by shoulder rivets 40 similar to the rivets 23 of the embodiment in Fig. 1. In the embodiment of Fig. 4 the focusing flux is concentrated by the discs H and J across the gap K between the flanges 38.

The focusing device of this invention provides a small diameter aperture for focusing the electron beam. The discs inside the tube guide the flux to the aperture. The discs cooperate with 10 The the flux producing beams, coil or magnet to facilitate the concentration of the flux at the aperture and increase the effect of the flux on the focusing of the electron stream.

The flux as it emanates from the flux producer may have an unsymmetrical nature. The conveying of the lines of force through the discs of this invention will tend to even out this lack of symmetry and thus sharpen the effect the focusing device has on the electron stream.

The discs inside the neck I!) are composed of a highly permeable material It is an advantage of this invention that the electrical force to provide .a given required flux at the electron stream is lowered. A further resultant advantage is a reduction in the demands on the flux producing parts. Through this invention a reduction in the amount of the necessary materials in the focusing device brings about an economy of materials with consequent conservation.

A further advantage of this invention as applied to television picture tubes is the improved quality of focusing. A more symmetrical flux in the focusing field causes the electron stream to produce a more circular spot on the fluorescent field. Moreover, flux leakages from the focusing device to other tube components such as the ion trap and deflection yoke, are minimized. A collateral advantage of this invention is that the disc or pole piece adjacent the electron gun can serve the dual purpose of transmitting and concentrating the focusing flux and also serving as the accelerating electrode or second grid of the electron gun assembly with all the consequent advantages.

The above described embodiments are for the purpose of illustration of this invention and it will be understood that various modifications may be made without departure from the spirit of this invention.

I claim:

1. A focusing device for a cathode ray tube having a glass wall with a cylindrical neck around an electron gun adapted to emit a steam of electrons comprising a flux source concentric with the cylindrical neck and adjacent the emitting end of the electron gun and extending longitudinally along the neck of the tube with the poles longitudinally spaced to provide lines of flux extending in a longitudinal direction to form concentric areas of flux lines around the central axis of the tube in front of the emitting end of the electron gun, a pair of axially spaced flux conducting members mounted on the emitting end of the electron gun and concentric with the flux source and in the flux field, said members having an outer diameter substantially equal to the diameter of the inner surface and being insertable within the neck of the tube, one of said members being mounted on the end of said electron gun and the other member having spring guides pressing against the inner surface of the neck to position each member concentrically within the neck, each member having a central opening and an outer portion formed in one continuous piece of thin metal from the periphery of the central opening concentrically with the axis of the neck to the periphery of the outer portion adjacent the end of said flux source to concentrate said flux across the edges of said opening, said openings being of the source size and longitudinally spaced along the central axis and each having a diameter from one quarter to one third the diameter of said neck and longitudinally spaced apart a distance substantially equal'to 5 slightly less than the diameter of said openings to form a concentric centrally shaped flux field between said members at said openings and around the path of the electron beam from said gun to force said electrons into a concentrated beam.

2. A focusing device as claimed in claim 1 wherein said flux source is outside of said neck and each member comprises a cylindrical member adjacent said inner surface and extending from a, pole end of said flux source to a radial portion extending inwardly to said opening.

3. A focusing device as claimed in claim 1 wherein flux source is outside of said neck and each member comprises a cylindrical member adjacent said inner surface and extending from a pole end of said flux to a conically shaped member extending inwardly to said opening.

WILLIAM F. STEERS.

REFERENCES CITED The following references are of record in the file of this patent:

Number 6 UNITED STATES PATENTS Name Date Lubcke Nov. 6, 1934 Bruche June 16, 1936 Ruska Jan. 10, 1939 Ploke Feb. 28, 1939 Farnsworth May 16, 1939 Schlesinger Jan. 30, 1940 Nicoll May 7, 1940 Holst Aug. 20, 1940 Boersch et a1. Oct. 21, 1941 Ruska Feb. 10, 1942 Borries et a1 Dec. 22, 1942 Coeterier May 2, 1944 Ramberg Feb. 20, 1945 Rudenberg Nov. 23, 1948 Liebmann Nov. 1, 1949 Reisner Apr. 4, 1950 Quam Dec. 12, 1950 Quam Dec. 12, 1950 Quam Dec. 12, 1950 

